OBJECTIVE: To achieve a better understanding of the structural basis of brain-endocrine interaction. METHODS: Tissues of the developing infundibulum (median eminence and infundibular stem) will be studied in a twofold approach: 1) Human fetuses will be used for electron microscopic (TEM) analysis of developmental changes in the infundibulum. Fetuses between 10 and 20 weeks of gestational age will be studied initially, with later and earlier stages to be examined at a later time. 2) Freeze-fracturing will be employed to study the tissue components of the infundibulum, first in adult rats, then in neonatal and fetal rats, and finally in the human fetus. This relatively new technique can provide different kinds of information especially as to membrane characteristics and interrelationships of the components of the infundibulum.